12 



CHARLES E. BILLS. 



tached ribbons blown in front of an electric fan, or to that of the 

 succession of waves obtained by shaking and twisting a number of 

 fixed ropes. In no case, however, even at the moment of the ces- 

 sation of undulatory motion, was it possible to observe in the 

 gullet the cilia themselves ; only their wave-like motion could be 



OpBtrtotilo faeuole 



Eecistose 



Pood Vaooole 

 Contractile Vacnole 



FIG. i. Camera lucida tracings of specimens of Paramecium caudatum 

 narcotized with propyl alcohol, intended to give especially the appearance 

 of the gullet as the animal turns through 180. The paramecia are heavily 

 narcotized, and the incorporation of food vacuoles is beginning to be retarded. 



A. View of paramecium in the position most frequently assumed when 

 quiet. The gullet is in semi-profile. Food particles are aggregated, but re- 

 main in the gullet. 



B. View of paramecium lying on its " side." The gullet is in full profile. 

 Food particles are not aggregated. 



C. View of paramecium from the aboral side turned through 180 with 

 reference to the position in (A). Food particles are aggregated, but remain 

 in the gullet. 



